Busch R, Hill C M, Hayball J D, Lamb J R, Rothbard J B
ImmuLogic Pharmaceutical Corporation, Palo Alto, CA 94304.
J Immunol. 1991 Aug 15;147(4):1292-8.
Class I and class II MHC glycoproteins are highly polymorphic molecules that bind antigenic peptides and present them on cell surfaces for recognition by T lymphocytes. Even though MHC polymorphism has long been known to affect both peptide binding and recognition by the TCR, the role of individual amino acids of MHC proteins in these interactions is poorly understood. To examine the effect of a small number of amino acid residues on T cell stimulation, B lymphoblastoid cell lines homozygous for the closely related DR1 subtypes, Dw1 and Dw20, and the DR4 subtypes, Dw4 and Dw14, were compared for their ability to present an immunogenic influenza hemagglutinin peptide (HA307-319) to an Ag-specific, DR1,4-restricted T cell clone. B cell lines expressing DR1 Dw20 and DR4 Dw14 presented HA307-319 much less efficiently than DR1 Dw1 and DR4 Dw4 and bound a biotinylated analogue of the same peptide less well. Analysis of DRB1 gene sequences suggested that polymorphism at residue 86 had a major effect on peptide binding. Differences in binding of a set of HA307-319 analogues biotinylated at each residue to cells expressing DR1 Dw1 and DR1 Dw20 suggested that the polymorphism affected the interactions of many peptide residues with the class II molecule. In inhibition assays, DR1 Dw1 and DR4 Dw4 were shown to differ from DR1 Dw20 and DR4 Dw14 in their length requirements for peptide binding. Using a larger panel of homozygous B cell lines expressing many class II haplotypes, a Ser-309 substituted HA307-319 analogue was shown to bind to most B cell lines expressing Val-86 containing alleles (including DR1 Dw20 and DR4 Dw14) but failed to bind most B cell lines expressing Gly-86 alleles (including DR1 Dw1 and DR4 Dw4). The results indicated that polymorphism at residue 86 influenced the specificity and affinity of peptide binding and affected the conformation of peptide-DR protein complexes without completely eliminating T cell recognition.
I类和II类主要组织相容性复合体（MHC）糖蛋白是高度多态性的分子，它们结合抗原肽并将其呈递在细胞表面以供T淋巴细胞识别。尽管长期以来已知MHC多态性会影响肽结合以及T细胞受体（TCR）的识别，但MHC蛋白的单个氨基酸在这些相互作用中的作用却知之甚少。为了研究少数氨基酸残基对T细胞刺激的影响，比较了密切相关的DR1亚型Dw1和Dw20以及DR4亚型Dw4和Dw14纯合的B淋巴母细胞系将免疫原性流感血凝素肽（HA307 - 319）呈递给抗原特异性、DR1,4限制性T细胞克隆的能力。表达DR1 Dw20和DR4 Dw14的B细胞系呈递HA307 - 319的效率远低于DR1 Dw1和DR4 Dw4，并且与相同肽的生物素化类似物结合能力也较差。对DRB1基因序列的分析表明，第86位残基的多态性对肽结合有重大影响。一组在每个残基处生物素化的HA307 - 319类似物与表达DR1 Dw1和DR1 Dw20的细胞结合的差异表明，这种多态性影响了许多肽残基与II类分子的相互作用。在抑制试验中，DR1 Dw1和DR4 Dw4在肽结合的长度要求上与DR1 Dw20和DR4 Dw14不同。使用一组表达多种II类单倍型的纯合B细胞系，显示一种Ser - 309取代的HA307 - 319类似物能与大多数表达含Val - 86等位基因的B细胞系（包括DR1 Dw20和DR4 Dw14）结合，但不能与大多数表达Gly - 86等位基因的B细胞系（包括DR1 Dw1和DR4 Dw4）结合。结果表明，第86位残基的多态性影响了肽结合的特异性和亲和力，并影响了肽 - DR蛋白复合物的构象，但并未完全消除T细胞识别。
